This application relates to and incorporates herein by reference Japanese Patent Applications No. 11-199253 filed on Jul. 13, 1999 and 2000-106997 filed on Apr. 7, 2000.
The present invention relates to a portable terminal device such as a cellular phone having illumination function for a key unit and a display unit.
Conventional cellular phones have respective key units and LCD display units on the front side. The key unit includes a plurality of keys for inputting numbers, characters, operation commands and the like. The display unit is for displaying various information in characters or in images. The key unit and the display unit also include backlights such as light-emitting diodes so that the key unit and the display unit may be illuminated in operation. The light emitting diodes are turned off after a predetermined time, e.g., 10 seconds, from the completion of operation of the key unit and the display unit thereby to save the energy of a built-in battery.
The cellular phone may have a character information display mode for displaying character information for electronic mails or bank account checking on its display unit. In this mode, the keys are operated frequently. If illumination control of the key unit and the display unit is effected simultaneously based on only the phone condition or the time lapse after completing phone operation, battery power consumption increases.
It is proposed in JP-A-11-154900 to enable manual predetermined setting of turning of f of either the display unit or the key unit. However, if turning off the key unit is set in advance, it becomes difficult to manipulate the keys in the darkness.
It is therefore an object of the present invention to provide a portable terminal device with illumination control which consumes less electric power.
According to the present invention, a portable terminal device such as a cellular phone comprises a key unit, a display unit, an illumination unit, and a light control circuit. The illumination unit first illuminates both the display unit and the key unit, but stops illuminating the key unit based on a display condition of the display unit to save power supplied by a built-in battery.
In an internet mode, the illumination of the key unit is stopped after a predetermined time, and the illumination of the display unit is maintained as long as the displayed information on the display unit is changing.
In a karaoke mode, the illumination of the key unit is stopped after a predetermined time, and the illumination of the display unit is maintained as long as music is produced, for instance, song words are displayed on the display unit.
In an electronic mail mode, the illumination of ten key part of the key unit is stopped when the terminal device is in a non-character/number input mode in a predetermined time, and illumination of the display unit and a function key part of the key unit is maintained in a character/number input mode in the predetermined time.